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 /******************************************************************************
  *
  * Module Name: utlock - Reader/Writer lock interfaces
  *
  *****************************************************************************/
 
 /******************************************************************************
  *
  * 1. Copyright Notice
  *
  * Some or all of this work - Copyright (c) 1999 - 2024, Intel Corp.
  * All rights reserved.
  *
  * 2. License
  *
  * 2.1. This is your license from Intel Corp. under its intellectual property
  * rights. You may have additional license terms from the party that provided
  * you this software, covering your right to use that party's intellectual
  * property rights.
  *
  * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
  * copy of the source code appearing in this file ("Covered Code") an
  * irrevocable, perpetual, worldwide license under Intel's copyrights in the
  * base code distributed originally by Intel ("Original Intel Code") to copy,
  * make derivatives, distribute, use and display any portion of the Covered
  * Code in any form, with the right to sublicense such rights; and
  *
  * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
  * license (with the right to sublicense), under only those claims of Intel
  * patents that are infringed by the Original Intel Code, to make, use, sell,
  * offer to sell, and import the Covered Code and derivative works thereof
  * solely to the minimum extent necessary to exercise the above copyright
  * license, and in no event shall the patent license extend to any additions
  * to or modifications of the Original Intel Code. No other license or right
  * is granted directly or by implication, estoppel or otherwise;
  *
  * The above copyright and patent license is granted only if the following
  * conditions are met:
  *
  * 3. Conditions
  *
  * 3.1. Redistribution of Source with Rights to Further Distribute Source.
  * Redistribution of source code of any substantial portion of the Covered
  * Code or modification with rights to further distribute source must include
  * the above Copyright Notice, the above License, this list of Conditions,
  * and the following Disclaimer and Export Compliance provision. In addition,
  * Licensee must cause all Covered Code to which Licensee contributes to
  * contain a file documenting the changes Licensee made to create that Covered
  * Code and the date of any change. Licensee must include in that file the
  * documentation of any changes made by any predecessor Licensee. Licensee
  * must include a prominent statement that the modification is derived,
  * directly or indirectly, from Original Intel Code.
  *
  * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
  * Redistribution of source code of any substantial portion of the Covered
  * Code or modification without rights to further distribute source must
  * include the following Disclaimer and Export Compliance provision in the
  * documentation and/or other materials provided with distribution. In
  * addition, Licensee may not authorize further sublicense of source of any
  * portion of the Covered Code, and must include terms to the effect that the
  * license from Licensee to its licensee is limited to the intellectual
  * property embodied in the software Licensee provides to its licensee, and
  * not to intellectual property embodied in modifications its licensee may
  * make.
  *
  * 3.3. Redistribution of Executable. Redistribution in executable form of any
  * substantial portion of the Covered Code or modification must reproduce the
  * above Copyright Notice, and the following Disclaimer and Export Compliance
  * provision in the documentation and/or other materials provided with the
  * distribution.
  *
  * 3.4. Intel retains all right, title, and interest in and to the Original
  * Intel Code.
  *
  * 3.5. Neither the name Intel nor any other trademark owned or controlled by
  * Intel shall be used in advertising or otherwise to promote the sale, use or
  * other dealings in products derived from or relating to the Covered Code
  * without prior written authorization from Intel.
  *
  * 4. Disclaimer and Export Compliance
  *
  * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
  * HERE. ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
  * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT, ASSISTANCE,
  * INSTALLATION, TRAINING OR OTHER SERVICES. INTEL WILL NOT PROVIDE ANY
  * UPDATES, ENHANCEMENTS OR EXTENSIONS. INTEL SPECIFICALLY DISCLAIMS ANY
  * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
  * PARTICULAR PURPOSE.
  *
  * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
  * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
  * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
  * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
  * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
  * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS
  * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
  * LIMITED REMEDY.
  *
  * 4.3. Licensee shall not export, either directly or indirectly, any of this
  * software or system incorporating such software without first obtaining any
  * required license or other approval from the U. S. Department of Commerce or
  * any other agency or department of the United States Government. In the
  * event Licensee exports any such software from the United States or
  * re-exports any such software from a foreign destination, Licensee shall
  * ensure that the distribution and export/re-export of the software is in
  * compliance with all laws, regulations, orders, or other restrictions of the
  * U.S. Export Administration Regulations. Licensee agrees that neither it nor
  * any of its subsidiaries will export/re-export any technical data, process,
  * software, or service, directly or indirectly, to any country for which the
  * United States government or any agency thereof requires an export license,
  * other governmental approval, or letter of assurance, without first obtaining
  * such license, approval or letter.
  *
  *****************************************************************************
  *
  * Alternatively, you may choose to be licensed under the terms of the
  * following license:
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions, and the following disclaimer,
  *    without modification.
  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  *    substantially similar to the "NO WARRANTY" disclaimer below
  *    ("Disclaimer") and any redistribution must be conditioned upon
  *    including a substantially similar Disclaimer requirement for further
  *    binary redistribution.
  * 3. Neither the names of the above-listed copyright holders nor the names
  *    of any contributors may be used to endorse or promote products derived
  *    from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Alternatively, you may choose to be licensed under the terms of the
  * GNU General Public License ("GPL") version 2 as published by the Free
  * Software Foundation.
  *
  *****************************************************************************/
 
 #include "acpi.h"
 #include "accommon.h"
 
 
 #define _COMPONENT          ACPI_UTILITIES
         ACPI_MODULE_NAME    ("utlock")
 
 
 /*******************************************************************************
  *
  * FUNCTION:    AcpiUtCreateRwLock
  *              AcpiUtDeleteRwLock
  *
  * PARAMETERS:  Lock                - Pointer to a valid RW lock
  *
  * RETURN:      Status
  *
  * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
  *
  ******************************************************************************/
 
 ACPI_STATUS
 AcpiUtCreateRwLock (
     ACPI_RW_LOCK            *Lock)
 {
     ACPI_STATUS             Status;
 
 
     Lock->NumReaders = 0;
     Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
     if (ACPI_FAILURE (Status))
     {
         return (Status);
     }
 
     Status = AcpiOsCreateMutex (&Lock->WriterMutex);
     return (Status);
 }
 
 
 void
 AcpiUtDeleteRwLock (
     ACPI_RW_LOCK            *Lock)
 {
 
     AcpiOsDeleteMutex (Lock->ReaderMutex);
     AcpiOsDeleteMutex (Lock->WriterMutex);
 
     Lock->NumReaders = 0;
     Lock->ReaderMutex = NULL;
     Lock->WriterMutex = NULL;
 }
 
 
 /*******************************************************************************
  *
  * FUNCTION:    AcpiUtAcquireReadLock
  *              AcpiUtReleaseReadLock
  *
  * PARAMETERS:  Lock                - Pointer to a valid RW lock
  *
  * RETURN:      Status
  *
  * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
  *              only the first reader acquires the write mutex. On release,
  *              only the last reader releases the write mutex. Although this
  *              algorithm can in theory starve writers, this should not be a
  *              problem with ACPICA since the subsystem is infrequently used
  *              in comparison to (for example) an I/O system.
  *
  ******************************************************************************/
 
 ACPI_STATUS
 AcpiUtAcquireReadLock (
     ACPI_RW_LOCK            *Lock)
 {
     ACPI_STATUS             Status;
 
 
     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
     if (ACPI_FAILURE (Status))
     {
         return (Status);
     }
 
     /* Acquire the write lock only for the first reader */
 
     Lock->NumReaders++;
     if (Lock->NumReaders == 1)
     {
         Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
     }
 
     AcpiOsReleaseMutex (Lock->ReaderMutex);
     return (Status);
 }
 
 
 ACPI_STATUS
 AcpiUtReleaseReadLock (
     ACPI_RW_LOCK            *Lock)
 {
     ACPI_STATUS             Status;
 
 
     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
     if (ACPI_FAILURE (Status))
     {
         return (Status);
     }
 
     /* Release the write lock only for the very last reader */
 
     Lock->NumReaders--;
     if (Lock->NumReaders == 0)
     {
         AcpiOsReleaseMutex (Lock->WriterMutex);
     }
 
     AcpiOsReleaseMutex (Lock->ReaderMutex);
     return (Status);
 }
 
 
 /*******************************************************************************
  *
  * FUNCTION:    AcpiUtAcquireWriteLock
  *              AcpiUtReleaseWriteLock
  *
  * PARAMETERS:  Lock                - Pointer to a valid RW lock
  *
  * RETURN:      Status
  *
  * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
  *              release the writer mutex associated with the lock. Acquisition
  *              of the lock is fully exclusive and will block all readers and
  *              writers until it is released.
  *
  ******************************************************************************/
 
 ACPI_STATUS
 AcpiUtAcquireWriteLock (
     ACPI_RW_LOCK            *Lock)
 {
     ACPI_STATUS             Status;
 
 
     Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
     return (Status);
 }
 
 
 void
 AcpiUtReleaseWriteLock (
     ACPI_RW_LOCK            *Lock)
 {
 
     AcpiOsReleaseMutex (Lock->WriterMutex);
 }

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